1. Field of the Invention
The invention relates to a kind of hydro bearing and its manufacturing method. It is applied to small-scale spindle motors. In particular, it has the effect of a hydrodynamic and hydrostatic hybrid type, and it is easy to process the hydrodynamic and hydrostatic hybrid bearing and its manufacturing method.
2. Related Art
A bearing is a kind of device that is applied on rotating machine parts, and is utilized for support, to decrease friction and to accept a load. It can be used, for example, in a spindle motor. The demand for bearing precision is increasing. Generally speaking, the bearing for which the most precision required is the ball bearing. However, this kind of bearing has some problems, such as noise, NRRO(Non-Repeatable Run Out) and high cost of miniaturization, and it would be unable to meet the demands of miniaturization and precision. In order to meet these demands, and to further reduce rotating friction, a hydro bearing with high precision in the future, low noise and strong anti-shock capability has been developed.
Generally speaking, there are two types of bearings: the hydrostatic hearing and hydrodynamic bearing. The hydrostatic bearing is normally a bearing with a hydro lubricant. When the motor rotates, it utilizes hydro pressure to support its shaft. If its shaft deviates, pressure should be added from the deviated side to make the shaft return to the correct position. However, since hydrostatic bearings usually contain a lot of lubricant, they are not suitable for small rotating machine parts that require high precision.
On the other hand, the hydrodynamic bearing is a bearing with tiny grooves located at the bearing's inner aperture. Within the grooves there is a lubricant (since the grooves are tiny, the quantity of lubricant is quite limited). When the shaft rotates, the lubricant inside the grooves is drawn and builds up hydrodynamic pressure to support the shaft at a centered position. However, since it is hydrodynamic, friction occurs when the shaft starts to rotate and pressure has not yet been built up. It is also very difficult to process the inner aperture inside the bearing, and difficult to control the processing precision (the grooves width is usually 100 μm, and the grooves' depth are even smaller) Moreover, there are problems with the lubricant seal and lubricant filling.
Aimed at these problems with hydrodynamic bearings, many different solutions have been suggested in previous cases, especially regarding processing methods for the tiny grooves in the bearing's inner aperture. For example, there are cutting processing, balling processing, plastic ejection, corrosion, combination and processing after cladding. However, whichever way is used for inner aperture processing, it is difficult to increase the precision and difficult to process, and problems relating to starting friction, lubricant seal and lubricant filling cannot be solved. Hence, the application of bearings on the small active motors, like CD-ROMs and hard discs, has always been restricted.